FIG. 4 shows an example of a configuration of a power combiner according to the related art. A power combiner 10′ according to the related art is configured to combine high-frequency powers such that the high-frequency powers Pl to Pn respectively input to first to n-th input terminals INl to INn are output from one output terminal OUT via transmission circuits Tl′ to Tn′ respectively connected to the first to n-th input terminals INl to INn.
The first to n-th input terminals INl to INn are respectively connected to one ends of resistances Rl to Rn in parallel with the respective corresponding transmission circuits T1′ to Tn′ and the other ends of the resistances Rl to Rn are connected to each other, so that the input terminals INl to INn are connected to each other through the resistances Rl to Rn respectively connected to the input terminals INl to INn.
In each of the transmission circuits Tl′ to Tn′, a first inductor (Ll1 to Ln1) and a second inductor (Ll2 to Ln2) are connected to each other in series and a connection point of the first inductor and the second inductor is grounded through a capacitor (Cl to Cn).
FIG. 5 shows another example of a configuration of a power combiner according to the related art. FIG. 5 is the same as FIG. 4, except for a configuration of each of transmission circuits Tl″ to Tn″. Specifically, each of the transmission circuits Tl″ to Tn″ is comprised of a first to n-th inductor Ll to Ln, a first capacitor (Cl1 to Cn1) provided between an input terminal-side of the first to n-th inductor Ll to Ln and an earth, and a second capacitor (Cl2 to Cn2) provided between an output terminal-side of the first to n-th inductor Ll to Ln and the earth.
Patent Document 1: Japanese Patent Application Publication H07-263993A
A high-frequency power feed system is configured to perform a processing treatment such as plasma etching for an object to be processed such as a semiconductor wafer, a liquid crystal substrate and the like, by using high-frequency power output from a high-frequency power supply device. In the high-frequency power supply device used for such a processing treatment, a plurality of amplifier circuits that outputs high-frequency powers and a power combiner that combines and outputs the high-frequency powers output from the plurality of amplifier circuits are used. If the power combiner as shown in FIG. 4 or FIG. 5 is used for the high-frequency power supply device used such a processing treatment, the high-frequency powers that are input to the input terminals INl to INn of the power combiner may become high-power.
In the power combiner as shown in FIG. 4 or FIG. 5, if the high-frequency powers input to the input terminals INl to INn become high-power, it is necessary to use a capacitor having excellent withstand voltage characteristics and excellent withstand current characteristics as regards the capacitors used in the transmission circuits Tl to Tn. As the capacitor having excellent withstand voltage characteristics and excellent withstand current characteristics is very expensive, the manufacturing cost of the power combiner is increased. The same can be said for a power divider having an opposite function to that of the power combiner.